Such an oath doesn't exist (look up "oath" on the web). Rather he—and I—broke an agreement (known as Standard Form 312) which was a condition of employment. It provides for civil or administrative penalties (e.g., losing a clearance or a job) for disclosing classified information: serious enough to keep nearly everyone quiet about...anything classified, no matter how illegal or dangerous.

The reason this matters is that Snowden, as he said to Gellman and as I've repeatedly said, did take a real "oath," just one oath, the same oath that every official in the government and every Congressperson takes as an oath of office. He and they "swore" ("or affirmed") "to support and defend the Constitution of the U.S., against all enemies, foreign and domestic."

They did not swear to support and defend or obey the President, or to keep secrets. But to support and defend, among other elements of the Constitution, the First, Fourth, Fifth and Sixth Amendments in the Bill of Rights, and Article I, section 8, on war powers. That's the oath that, as Snowden correctly said to Gellman, he upheld (as I would say I eventually did) and that Clapper and Alexander broke (along with most members of Congress).

As Snowden and I discovered, that oath turns out to be often in conflict with the secrecy agreements that he and I signed, and which we later chose to violate in support of our oath.